The present invention relates generally to the field of lubrication and more particularly to centralized lubrication systems for feeding lubricant in predetermined quantities to a plurality of points of use such as bearings and the like.
One well known centralized lubrication system, commonly referred to as a single-line system, involves one or more series feeders in each of which is formed a plurality of cylindrical bores arranged in side-by-side relation. A piston or plunger is reciprocally carried in each of the bores. A lubricant inlet is provided in each series feeder for connection to a single lubricant supply line which delivers lubricant under pressure from a suitable source such as a positive displacement pump. A plurality of lubricant outlets are provided in each series feeder for connection respectively to a point of utilization or to another series feeder. By virtue of the arrangement of the hydraulic circuitry within the series feeders, and the valving action caused by movement of the pistons, the pressurized lubricant being supplied to each of the series feeders has the effect of reciprocating the pistons thereof serially and in a predetermined sequence. As a consequence of this hydraulic circuitry the pistons are hydraulically interlocked and the operation of the feeders and the movement of each of the pistons is dependent upon the continued movement of each of the other pistons. Thus if any one of the pistons is prevented from moving through its full stroke, due to blockage of its respective lubricant discharge line, for example, the movement of all of the pistons is prevented.
Such feeders, a typical embodiment of which is shown in Harter U.S. Pat. No. 2,792,911, are employed in a variety of centralized lubrication systems, that is, systems which supply lubricant from a single source to a plurality of points of use. One of the principal advantages of series feeders lies in the ease with which the cyclic operation thereof can be monitored.
For example, since each piston in each feeder must move a full stroke before the next succeeding piston can move, a "fault" signal for the entire feeder (or for a number of feeders, if they are connected in series) can be obtained merely by monitoring the movement of a single piston. Thus the series feeder is particularly amenable to the utilization of a relatively simple and inexpensive central monitor system.
Another advantage in the use of series feeders involves the manner in which the pressurized lubricant is supplied to the feeder. Since the valving action of the pistons themselves produces cyclic operation, the pistons are moved back and forth in their respective bores even through only a single lubricant supply line connects the feeder to the lubricant pump. Were it not for such valving action of the pistons and attendant hydraulic circuitry, it would be necessary to connect the pump to the feeder by means of two lines, with the pressurization of the lines being alternated, in order to effect reciprocal movement of the pistons.
Another well known centralized lubrication system is commonly referred to as a lubricant injector system. A typical system includes a plurality of injectors each of which comprises a single piston which expels a predetermined quantity of lubricant to a single point of use. Known lubricant injectors are incapable of sequential operation and thus in a lubrication system which services a number of lubrication points, each of the injectors is connected "in parallel" with the lubrication pump. The piston or plunger mechanisms in the various injectors are spring biased to a return or retracted position, after they have been moved under pressure to a lubricant displacement position to displace and expel lubricant from their respective outlets to points of utilization. Each of the injectors returns lubricant back through the lubricant supply line as its piston moves back to its retracted position, and this accumulation of lubricant which must be forced back through the supply line upon the completion of each lubrication cycle generally precludes the use of grease and other heavy lubricants in a lubricant injector system.
Since prior art lubricant injectors generally are not sequentially operable nor hydraulically interlocked they are actuated by lubricant supply pressure in a random pattern rather than in sequence, with the injector which is subjected to the lowest resistance or back pressure being activated first, then the injector subjected to the next lowest back pressure and so forth. Since the movement of each piston is independent of the movement of each of the other pistons, a simple central monitor system, detecting movement of only a single piston, cannot be used to monitor the movement of all the pistons. Instead a separate monitor system is required for each of the various lubricant injectors in a given system, if the operation of the entire system is to be monitored.
Furthermore, as a result of the significant amount of lubricant which must be forced back into the lubricant supply line at the conclusion of each lubrication cycle, central systems using lubricant injectors have been generally limited to the use of light oils, as cotrasted with grease and other heavy lubricants.
There is, however, at least one important advantage of lubrication system which employs lubricant injectors as opposed to series feeders. In an injector system, the number of injectors can be easily increased merely by connecting additional injectors to the main lubricant supply line. It is not necessary to disconnect and re-pipe any of the other injectors. In a system which utilizes series feeders, however, it is generally necessary to disassemble and reassemble at least portions of the feeder, or to add certain manifolding apparatus, to accommodate additional lubricant points of use.
The present invention involves the development of an improved centralized lubrication system as well as a lubricant injector which can be hydraulically interlocked and thus actuated in sequence when used in multiples to lubricate plurality of lubrication points. Further, more, only a relatively minor quantity of lubricant must be forced back through the lubricant supply line at the conclusion of each lubrication cycle. Thus, a centralized lubrication system employing my new injector would enjoy the advantages of a system using series feeders (hydraulic interlock, sequential operation and use of grease and other heavy lubricants) as well as the advantages of a system utilizing injectors (ease of "adding on"). In addition, and particularly in respect of the preferred embodiment of my invention, the manufacturing cost of injectors can be substantially reduced, thereby enabling centralized lubrication systems to be employed in a variety of applications which hitherto could not economically justify the use of central systems.